[PATCH net-next 2/2] macvlan: no longer rely on RTNL in macvlan_fill_info()
From: Eric Dumazet <edumazet@google.com>
Date: 2026-07-01 08:22:20
Subsystem:
networking drivers, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Add READ_ONCE()/WRITE_ONCE() annotations on vlan->mode, vlan->flags, vlan->bc_queue_len_req and port->bc_cutoff. Fill IFLA_MACVLAN_MACADDR_DATA nested attribute and compute on the fly the precise number of elements we put in it, to fill an accurate IFLA_MACVLAN_MACADDR_COUNT attribute as some user space applications could depend on its value and the attributes order. Signed-off-by: Eric Dumazet <edumazet@google.com> --- drivers/net/macvlan.c | 71 +++++++++++++++++++++++++++++-------------- 1 file changed, 48 insertions(+), 23 deletions(-)
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 8b69cc9b70f98d7991110f5eda76d58d5d96fa81..9a4bc99dbf53b5f2cd6345f0af899f56fdb3a46b 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c@@ -171,7 +171,7 @@ static int macvlan_hash_add_source(struct macvlan_dev *vlan, RCU_INIT_POINTER(entry->vlan, vlan); h = &port->vlan_source_hash[macvlan_eth_hash(addr)]; hlist_add_head_rcu(&entry->hlist, h); - vlan->macaddr_count++; + WRITE_ONCE(vlan->macaddr_count, vlan->macaddr_count + 1); return 0; }
@@ -402,7 +402,7 @@ static void macvlan_flush_sources(struct macvlan_port *port, if (rcu_access_pointer(entry->vlan) == vlan) macvlan_hash_del_source(entry); - vlan->macaddr_count = 0; + WRITE_ONCE(vlan->macaddr_count, 0); } static void macvlan_forward_source_one(struct sk_buff *skb,
@@ -874,7 +874,7 @@ static void update_port_bc_cutoff(struct macvlan_dev *vlan, int cutoff) if (vlan->port->bc_cutoff == cutoff) return; - vlan->port->bc_cutoff = cutoff; + WRITE_ONCE(vlan->port->bc_cutoff, cutoff); macvlan_recompute_bc_filter(vlan); }
@@ -1427,7 +1427,7 @@ static int macvlan_changelink_sources(struct macvlan_dev *vlan, u32 mode, entry = macvlan_hash_lookup_source(vlan, addr); if (entry) { macvlan_hash_del_source(entry); - vlan->macaddr_count--; + WRITE_ONCE(vlan->macaddr_count, vlan->macaddr_count - 1); } } else if (mode == MACVLAN_MACADDR_FLUSH) { macvlan_flush_sources(vlan->port, vlan);
@@ -1653,7 +1653,8 @@ static int macvlan_changelink(struct net_device *dev, } if (data && data[IFLA_MACVLAN_BC_QUEUE_LEN]) { - vlan->bc_queue_len_req = nla_get_u32(data[IFLA_MACVLAN_BC_QUEUE_LEN]); + WRITE_ONCE(vlan->bc_queue_len_req, + nla_get_u32(data[IFLA_MACVLAN_BC_QUEUE_LEN])); update_port_bc_queue_len(vlan->port); }
@@ -1676,10 +1677,12 @@ static int macvlan_changelink(struct net_device *dev, static size_t macvlan_get_size_mac(const struct macvlan_dev *vlan) { - if (vlan->macaddr_count == 0) + unsigned int macaddr_count = READ_ONCE(vlan->macaddr_count); + + if (!macaddr_count) return 0; return nla_total_size(0) /* IFLA_MACVLAN_MACADDR_DATA */ - + vlan->macaddr_count * nla_total_size(sizeof(u8) * ETH_ALEN); + + macaddr_count * nla_total_size(sizeof(u8) * ETH_ALEN); } static size_t macvlan_get_size(const struct net_device *dev)
@@ -1702,53 +1705,75 @@ static int macvlan_fill_info_macaddr(struct sk_buff *skb, const int i) { struct hlist_head *h = &vlan->port->vlan_source_hash[i]; - struct macvlan_source_entry *entry; + const struct macvlan_source_entry *entry; + int cnt = 0; - hlist_for_each_entry_rcu(entry, h, hlist, lockdep_rtnl_is_held()) { + hlist_for_each_entry_rcu(entry, h, hlist) { if (rcu_access_pointer(entry->vlan) != vlan) continue; if (nla_put(skb, IFLA_MACVLAN_MACADDR, ETH_ALEN, entry->addr)) - return 1; + return -EMSGSIZE; + cnt++; } - return 0; + return cnt; } static int macvlan_fill_info(struct sk_buff *skb, const struct net_device *dev) { - struct macvlan_dev *vlan = netdev_priv(dev); + const struct macvlan_dev *vlan = netdev_priv(dev); struct macvlan_port *port = vlan->port; - int i; - struct nlattr *nest; + unsigned int macaddr_count = 0; + struct nlattr *nest, *attr; + int bc_cutoff, cnt, i; - if (nla_put_u32(skb, IFLA_MACVLAN_MODE, vlan->mode)) + rcu_read_lock(); + if (nla_put_u32(skb, IFLA_MACVLAN_MODE, READ_ONCE(vlan->mode))) goto nla_put_failure; - if (nla_put_u16(skb, IFLA_MACVLAN_FLAGS, vlan->flags)) + + if (nla_put_u16(skb, IFLA_MACVLAN_FLAGS, READ_ONCE(vlan->flags))) goto nla_put_failure; - if (nla_put_u32(skb, IFLA_MACVLAN_MACADDR_COUNT, vlan->macaddr_count)) + + attr = nla_reserve(skb, IFLA_MACVLAN_MACADDR_COUNT, sizeof(u32)); + if (!attr) goto nla_put_failure; - if (vlan->macaddr_count > 0) { + + if (READ_ONCE(vlan->macaddr_count) > 0) { nest = nla_nest_start_noflag(skb, IFLA_MACVLAN_MACADDR_DATA); if (nest == NULL) goto nla_put_failure; for (i = 0; i < MACVLAN_HASH_SIZE; i++) { - if (macvlan_fill_info_macaddr(skb, vlan, i)) + cnt = macvlan_fill_info_macaddr(skb, vlan, i); + if (cnt < 0) goto nla_put_failure; + macaddr_count += cnt; } - nla_nest_end(skb, nest); + if (!macaddr_count) + nla_nest_cancel(skb, nest); + else if (nla_nest_end_safe(skb, nest) < 0) + goto nla_put_failure; } - if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN, vlan->bc_queue_len_req)) + *(u32 *)nla_data(attr) = macaddr_count; + + if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN, + READ_ONCE(vlan->bc_queue_len_req))) goto nla_put_failure; + if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN_USED, READ_ONCE(port->bc_queue_len_used))) goto nla_put_failure; - if (port->bc_cutoff != 1 && - nla_put_s32(skb, IFLA_MACVLAN_BC_CUTOFF, port->bc_cutoff)) + + bc_cutoff = READ_ONCE(port->bc_cutoff); + if (bc_cutoff != 1 && + nla_put_s32(skb, IFLA_MACVLAN_BC_CUTOFF, bc_cutoff)) goto nla_put_failure; + + rcu_read_unlock(); return 0; nla_put_failure: + rcu_read_unlock(); return -EMSGSIZE; }
--
2.55.0.rc0.799.gd6f94ed593-goog